Viscose spinning process



Emil Hubert, Dessau-Zleblgk, Ado]! Hamann', Wolten Krels Bitterteld, and Karl Weisbrod, Dessam'Gei-many, assignors, by memo assignments, to N. Y.

No Drawing.

3 Claims.

This invention relates to a spinning process for viscose rayon.

It is known that artificial threads of very good.

physical constants, especially high tenacity, can

be produced by stretching viscose threads in-a These known processes have the disadvantage that they require strongly acid baths for attaining good results, so that in practice they give rise to difliculties of various kinds. Besides the use of these strong acid baths it has been proposed to attain similar efiects by using sulphuric acid solutions of especially low percentage strength, for example 0.5-7 per cent oif sulphuric acid (British Patent No. 309,053) However, these baths have the disadvantage that the plastic condition of the thread persists for only a few seconds so that it is difilcult to be sure of taking advantage of this transitory condition for the stretching.

The present invention is based on the observation that a plasticizing agent may be added to the coagulation bath with the result that the threads obtained can be well stretched and are then of good tenacity.

The invention consists in a process in which the threads are coagulated in a bath free of acid and containing a non-acid plasticizing agent, for instance urea, thiourea, ammonium thiocyanate or the like, the coagulated thread being stretched.

and finally decomposed to cellulose hydrate.

Preferably the coagulation bath should beone =containing not more than ,50 per cent of water.

.jigThe decomposition to cellulose hydrate may occur under stretching or wholly without stretching; for example after the thread has been cut into staple fiber. As decomposing baths there may be solutions of acids alone or of acids and salts, tor lnstance the known Miiller bath. The decompositipnmay also be a thermal effect, for example the;t hr ead be subjected to a hot liquid or hot vapor rasca especially useful in case oi. cut staple. fiber.

Walther H. Duisberg, New York,

Application June 6, 1939, Serial No.

In Germany June I, 1938- The following examples illustrate the invention:

Example 1.From a. normally ripened viscose having for example 7.5 per cent of cellulose and 6.5 per cent of alkali there is spun a thread having a single titer of 2.6 denier from a spinneret having 120 perforations each of 0.08 millimeter diameter into a bath containing 8.5 per cent of NazSO4, 16 per cent of (NH-0:804 and 39 per cent of urea the bath having a temperature of 60C. The threads issuing from this .bathare drawn over glass rods arranged to afiord a zig-zag path, thedraught being meters per minute.

The coagulated and stretched threads are cut to staple length and decomposed in boiling sodium sulphate solution. The staple fibers are desulfurized in the usual manner and then soaped. 'Ihe fibers thus spun have a good extension and a very good tenacity: V a Dry tenacity: 3.8 per denier extension 19 per cent.

Wet tenacity: 2.74 per-denier.

The coagulation bath may have a composition different from that described in example. Preferably however the bath should not contain more than per cent oi water. Baths oi the following composition also give good results: 5.5 per cent of NaeSOr, 19 per cent (NHAMSGQ,

34 per cent urea or 15 per cent of NazSOs, 9 per cent 02804,

35 per cent of urea.

E:cample 2.+-A thread of single titer 2 (spin= neret having 128 perforations each of 0.08 mil- 'limeter diameter) is spun from a normally ripened cellulose containing 7.5 per cent of cellulose and 6.5 per cent of alkali in a bath containing 10 per cent of NazS04, 13 per cent of (NH4) 2504 andas per cent of urea maintained at,

50 C. The thread is stretched over several glass rods set to form a zig-zag path and is wound at the rate of 50 meters per minute on a spool. For decomposing the threads to cellulose hydrate the spool runs during me spinning in an acid upper bath containing 13 per cent of sulfuric acid and- -28 per cent of sodium sulfate. The acid spool is further treated in the usual manner, for example de-acidified in a suction washer and desuliurized in the form of hanks and then bleached and soaped. I Dry tenacity: 3.3 per denier, extension 6 per cent.

Wet tenacity: 2.1 per denier, extension 5.5 per monium sulfate and about 33 per cent of urea; stretching said threads while in plastic condition and decomposing the cellulose xanthate to cellulose hydrate.

2. A process of producing viscose threads which comprises spinning viscose-into an aqueous acid free bath incapable of entirely decomposing the cellulose xanthate, but capable of coagulating the viscose, said bath containing sodium sulfate, ammonium sulfate .and urea in such quantities as to amount to more than 50% of the bath, stretching the threads while in plastic condition and decomposing the cellulose xanthate to cellulose hydrate.

3. A process of producing viscose threads which comprises spinning viscose into an aqueous bath free from acids, incapable of decomposing the cellulose xanthate but capable of coagulating the viscose, said bath containing sodium sulfate, ammonium sulfate and urea in such quantities as to amount to more than 50% of the bath, stretching the threads after leaving the bath, cutting oil the threads in staples and decomposing the staple wastein hot solution or hot vapors.

EMIL HUBERT. ADOLF HAMANN. KARL WEISBRDD. 

